title: The spindle assembly function of Caenorhabditis elegans katanin does not require microtubule-severing activity.
abstract: Katanin is a heterodimeric microtubule-severing protein that is conserved among eukaryotes. Loss-of-function mutations in the Caenorhabditis elegans katanin catalytic subunit, MEI-1, cause specific defects in female meiotic spindles. To determine the relationship between katanin's microtubule-severing activity and its role in meiotic spindle formation, we analyzed the MEI-1(A338S) mutant. Unlike wild-type MEI-1, which mediated disassembly of microtubule arrays in Xenopus fibroblasts, MEI-1(A338S) had no effect on fibroblast microtubules, indicating a lack of microtubule-severing activity. In C. elegans, MEI-1(A338S) mediated assembly of extremely long bipolar meiotic spindles. In contrast, a nonsense mutation in MEI-1 caused assembly of meiotic spindles without any poles as assayed by localization of the spindle-pole protein, ASPM-1. These results indicated that katanin protein, but not katanin's microtubule-severing activity, is required for assembly of acentriolar meiotic spindle poles. To understand the nonsevering activities of katanin, we characterized the N-terminal domain of the katanin catalytic subunit. The N-terminal domain was necessary and sufficient for binding to the katanin regulatory subunit. The katanin regulatory subunit in turn caused a dramatic change in the microtubule-binding properties of the N-terminal domain of the catalytic subunit. This unique bipartite microtubule-binding structure may mediate the spindle-pole assembly activity of katanin during female meiosis.
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA. fjmcnally@ucdavis.edu
authors.forename: Karen Perry
authors.initials: KP
authors.lastname: McNally
authors.forename: Francis J
authors.initials: FJ
authors.lastname: McNally
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000074201:Katanin; D008540:Meiosis; D008870:Microtubules / Q000201:enzymology* / Q000235:genetics; D008938:Mitosis; D009154:Mutation; D011485:Protein Binding; D008941:Spindle Apparatus / Q000201:enzymology* / Q000235:genetics; D014981:Xenopus / Q000235:genetics
chemical_list: C539484:Aspm-1 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D000251:Adenosine Triphosphatases; C086678:MEI-1 protein, C elegans; D000074201:Katanin